Laser-marking systems are now in common use for marking materials such as metals, glass, wood, and plastic. Lasers used in such marking systems include diode-pumped solid-state lasers, fiber-lasers, and carbon dioxide (CO2) lasers. Typically a beam from whatever laser is used in the system is steered by a two-axis galvanometer and focused by f-theta optics onto a surface of an object being marked.
Special materials have been developed, and are commercially available, for accepting laser-radiation to allow high-speed, high-volume, writing of labels with a laser marking system. One such material is “Laser Markable Label Material 7847” available from 3M Corporation of Minneapolis, Minnesota. This material is a three-layer polymer material having an outer layer of a black material to facilitate absorption of laser-radiation. Beneath the black material is a layer of white material which is exposed when the black material is ablated away by laser-radiation. The black and white material layers are backed by an adhesive layer. These three layers are supported on a carrier from which an adhesive backed label can be peeled when complete. The white material can be laser-cut to define the bounds of the label and allow such peeling. Other materials include black-anodized metal (aluminum) foil, organic materials used in electronics packaging and printed circuit boards, and white paper impregnated with a dye having an absorption band in the near infrared region of the electromagnetic spectrum for absorbing NIR laser-radiation. These materials are conveniently supplied in the form of rolls of tape, so that large numbers of separate labels can be generated without having to reload material in the label maker.
Even the least expensive laser-marking system designed for these label materials has a cost at least about two orders of magnitude greater than a computer peripheral paper-label printer such as an inkjet printer. Because of this, such a system is beyond the means of the majority of smaller industrial or commercial users. This is somewhat unfortunate, as these laser-markable materials have significant advantages over inkjet-printed labels in terms of ruggedness and durability. Accordingly, there is a need for a significant reduction in the cost of systems for printing such laser-markable materials.